Description: An existing ice core sulfate dataset was processed to identify the largest volcanic eruption peaks of the last 203 kyr. The dataset used consisted of high resolution sulfate data (previously archived at https://www.ncdc.noaa.gov/paleo-search/study/31332), analysed by fast ion chromatography, from the EPICA Dome C ice core. To process the data, a background was removed, and fluxes of sulfate deposited were calculated for every peak above background, using a consistent method that corrects for ice accumulation rate and thinning. A threshold flux of 20 mg m⁻² yr⁻¹ has been used to ensure that only peaks of definite volcanic origin are listed. This dataset lists the depths, ages (AICC2012 age model) and fluxes of each peak with a flux 〉 20 mg m⁻² yr⁻¹.

Description: Multiple peaks in sulfate concentration in ice cores have been identified as potential candidates for the ~74 ka Toba supereruption. The sulfur isotopic composition of sulfate preserved in two EPICA Antarctic ice cores, EDML and EDC, for 11 of the candidates has been analysed at high temporal resolution for mass-independent fractionation (MIF) using multi-collector inductively coupled plasma mass spectrometry. S-MIF signals preserved in volcanic sulfate are indicative of stratospheric eruptions due to sulfur aerosols being exposed to ultraviolet radiation when erupted into and above the ozone layer and subsequently undergoing photochemical reactions. Sulfur aerosols in the stratosphere will have longer residence times than those in the troposphere and will scatter incoming solar radiation. This data set includes the eruption, sample type, depths, ages (using the AICC2012 age model), sulfate concentration (determined by ion chromatography) and isotopic composition data (δ34S, δ33S, Δ33S) and their associated errors.

Description: A chronology called EDML1 has been developed for the EPICA ice core from Dronning Maud Land (EDML). EDML1 is closely interlinked with EDC3, the new chronology for the EPICA ice core from Dome-C (EDC) through a stratigraphic match between EDML and EDC that consists of 322 volcanic match points over the last 128 ka. The EDC3 chronology comprises a glaciological model at EDC, which is constrained and later selectively tuned using primary dating information from EDC as well as from EDML, the latter being transferred using the tight stratigraphic link between the two cores. Finally, EDML1 was built by exporting EDC3 to EDML. For ages younger than 41 ka BP the new synchronized time scale EDML1/EDC3 is based on dated volcanic events and on a match to the Greenlandic ice core chronology GICC05 via 10Be and methane. The internal consistency between EDML1 and EDC3 is estimated to be typically ~6 years and always less than 450 years over the last 128 ka (always less than 130 years over the last 60 ka), which reflects an unprecedented synchrony of time scales. EDML1 ends at 150 ka BP (2417 m depth) because the match between EDML and EDC becomes ambiguous further down. This hints at a complex ice flow history for the deepest 350 m of the EDML ice core.

Description: Interpretation of ice core marine chemistry is often ambiguous because multiple processes influence the signal preserved. Using a chemical transport model, we investigate the relative influence of sea ice and meteorology changes on sea salt sodium records from Arctic ice cores. For inland Greenland cores, our simulations suggest that the sodium budget is dominated by the open ocean source and that inter-annual variability is primarily driven by meteorological conditions not the strength of aerosol emissions. In contrast, for coastal high Arctic cores, the sea ice surface is the principal aerosol source, with inter-annual variability strongly linked to aerosol emissions. High Arctic ice cores may therefore record decadal to centennial scale Holocene sea ice variability. However, any relationship between ice core sodium and sea ice may depend on how sea ice thickness or seasonality impacts sea salt emissions. Field-based observations are urgently required to constrain this. Simulations performed using Cambridge p-TOMCAT chemical transport model which represents the emission, transport and deposition of sea salt aerosol sourced from the open ocean (OOSS) and sea ice surface (SISS). p-TOMCAT is a 3D global model with a spatial resolution of 2.8° x 2.8° across 31 vertical sigma-pressure levels driven by ERA-Interim wind, temperature and humidity fields and HadISST-derived sea ice fraction.

Description: Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring in Antarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate of changes in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosol source. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes in the glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of the Southern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of the atmospheric dust concentration changes in Antarctica, while factor 5-10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. Dust emissions, hence environmental conditions in Patagonia, were very similar during the last two glacials and interglacials, respectively, despite 2-4 °C warmer temperatures recorded in Antarctica during the penultimate interglacial than today. 2-3 times higher sea salt fluxes found in both ice cores in the glacial compared to the Holocene are difficult to reconcile with a largely unchanged transport intensity and the distant open ocean source. The substantial glacial enhancements in sea salt aerosol fluxes can be readily explained assuming sea ice formation as the main sea salt aerosol source with a significantly larger expansion of (summer) sea ice in the Weddell Sea than in the Indian Ocean sector. During the penultimate interglacial, our sea salt records point to a 50% reduction of winter sea ice coverage compared to the Holocene both in the Indian and Atlantic Ocean sector of the SO. However, from 20 to 80 ka before present sea salt fluxes show only very subdued millennial changes despite pronounced temperature fluctuations, likely due to the large distance of the sea ice salt source to our drill sites.

Description: Sea ice and dust flux increased greatly in the Southern Ocean during the last glacial period. Palaeorecords provide contradictory evidence about marine productivity in this region, but beyond one glacial cycle, data were sparse. Here we present continuous chemical proxy data spanning the last eight glacial cycles (740,000 years) from the Dome C Antarctic ice core. These data constrain winter sea-ice extent in the Indian Ocean, Southern Ocean biogenic productivity and Patagonian climatic conditions. We found that maximum sea-ice extent is closely tied to Antarctic temperature on multi-millennial timescales, but less so on shorter timescales. Biological dimethylsulphide emissions south of the polar front seem to have changed little with climate, suggesting that sulphur compounds were not active in climate regulation. We observe large glacial-interglacial contrasts in iron deposition, which we infer reflects strongly changing Patagonian conditions. During glacial terminations, changes in Patagonia apparently preceded sea-ice reduction, indicating that multiple mechanisms may be responsible for different phases of CO2 increase during glacial terminations. We observe no changes in internal climatic feedbacks that could have caused the change in amplitude of Antarctic temperature variations observed 440,000 years ago.